Palladium-catalyzed C-N and C-O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols.

Simple and efficient procedures for palladium-catalyzed cross-coupling reactions of N-substituted 4-bromo-7-azaindole (1H-pyrrole[2,3-b]pyridine), with amides, amines, amino acid esters and phenols through C-N and C-O bond formation have been developed. The C-N cross-coupling reaction of amides, amines and amino acid esters takes place rapidly by using the combination of Xantphos, Cs(2)CO(3), dioxane and palladium catalyst precursors Pd(OAc)(2)/Pd(2)(dba)(3). The combination of Pd(OAc)(2), Xantphos, K(2)CO(3) and dioxane was found to be crucial for the C-O cross-coupling reaction. This is the first report on coupling of amides, amino acid esters and phenols with N-protected 4-bromo-7-azaindole derivatives.

Pd/C-mediated synthesis of indoles in water.

We describe the utility of a Pd/C-Cu mediated method in the synthesis of 2,5-disubstituted indoles in water via a coupling-cyclization strategy. Further application of this methodology has been demonstrated in the preparation of a target indole derivative via a 7-step process the key step being the Pd/C-mediated coupling reaction.

Fine-tuning of a ferrocene[porphyrin]ITO redox cascade for efficient sequential electron transfer commenced by an S2 photoexcited special-pair mimic.

A systematic series of ferrocene/porphyrin redox cascade architectures was assembled through a slipped-cofacial porphyrin dimer on ITO electrode in optimizing the anodic photocurrent generation to perform the highest quantum yield compared to reported values on ITO electrodes.

Efficient charge injection from the S2 photoexcited state of special-pair mimic porphyrin assemblies anchored on a titanium-modified ITO anode.

A novel surface fabrication methodology has been accomplished, aimed at efficient anodic photocurrent generation by a photoexcited porphyrin on an ITO (indium-tin oxide) electrode. The ITO electrode was submitted to a surface sol-gel process with titanium n-butoxide in order to deposit a titanium monolayer. Subsequently, porphyrins were assembled as monolayers on the titanium-treated ITO surface via phosphonate, isophthalate, and thiolate groups. Slipped-cofacial porphyrin dimers, the so-called artificial special pair at the photoreaction center, were organized through imidazolyl-to-zinc complementary coordination of imidazolylporphyrinatozinc(II) units, which were covalently immobilized by ring-closing olefin metathesis of allyl side chains. The modified surfaces were analyzed by means of X-ray photoelectron spectroscopy. Photoirradiation of the porphyrin dimer generated a large anodic photocurrent in aqueous electrolyte solution containing hydroquinone as an electron sacrificer, due to the small reorganization energy of the dimer. The use of different linker groups led to significant differences in the efficiencies of anodic photocurrent generation. The apparent flat-band potentials evaluated from the photocurrent properties at various pH values and under biased conditions imply that the band structure of the ITO electrode is modified by the anchoring species. The quantum yield for the anodic photocurrent generation by photoexcitation at the Soret band is increased to 15 %, a surprisingly high value without a redox cascade structure on the ITO electrode surface, while excitation at the Q band is not so significant. Extensive exploration of the photocurrent properties has revealed that hot injection of the photoexcited electron from the S2 level into the conduction band of the ITO electrode takes place before internal conversion to the S1* state, through the strong electronic communication of the phosphonyl anchor with the sol-gel-modified ITO surface.